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De Falco E, Solcà M, Bernasconi F, Babo-Rebelo M, Young N, Sammartino F, Tallon-Baudry C, Navarro V, Rezai AR, Krishna V, Blanke O. Single neurons in the thalamus and subthalamic nucleus process cardiac and respiratory signals in humans. Proc Natl Acad Sci U S A 2024; 121:e2316365121. [PMID: 38451949 PMCID: PMC10945861 DOI: 10.1073/pnas.2316365121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 01/16/2024] [Indexed: 03/09/2024] Open
Abstract
Visceral signals are constantly processed by our central nervous system, enable homeostatic regulation, and influence perception, emotion, and cognition. While visceral processes at the cortical level have been extensively studied using non-invasive imaging techniques, very few studies have investigated how this information is processed at the single neuron level, both in humans and animals. Subcortical regions, relaying signals from peripheral interoceptors to cortical structures, are particularly understudied and how visceral information is processed in thalamic and subthalamic structures remains largely unknown. Here, we took advantage of intraoperative microelectrode recordings in patients undergoing surgery for deep brain stimulation (DBS) to investigate the activity of single neurons related to cardiac and respiratory functions in three subcortical regions: ventral intermedius nucleus (Vim) and ventral caudalis nucleus (Vc) of the thalamus, and subthalamic nucleus (STN). We report that the activity of a large portion of the recorded neurons (about 70%) was modulated by either the heartbeat, the cardiac inter-beat interval, or the respiration. These cardiac and respiratory response patterns varied largely across neurons both in terms of timing and their kind of modulation. A substantial proportion of these visceral neurons (30%) was responsive to more than one of the tested signals, underlining specialization and integration of cardiac and respiratory signals in STN and thalamic neurons. By extensively describing single unit activity related to cardiorespiratory function in thalamic and subthalamic neurons, our results highlight the major role of these subcortical regions in the processing of visceral signals.
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Affiliation(s)
- Emanuela De Falco
- Laboratory of Cognitive Neuroscience, School of Life Sciences, Neuro-X Institute and Brain Mind Institute, École Polytechnique Fédérale de Lausanne, Lausanne1015, Switzerland
- Department of Neuroscience, Rockefeller Neuroscience Institute–West Virginia University, Morgantown, WV26505
| | - Marco Solcà
- Laboratory of Cognitive Neuroscience, School of Life Sciences, Neuro-X Institute and Brain Mind Institute, École Polytechnique Fédérale de Lausanne, Lausanne1015, Switzerland
- Department of Psychiatry, University Hospital Geneva, Geneva1205, Switzerland
| | - Fosco Bernasconi
- Laboratory of Cognitive Neuroscience, School of Life Sciences, Neuro-X Institute and Brain Mind Institute, École Polytechnique Fédérale de Lausanne, Lausanne1015, Switzerland
| | - Mariana Babo-Rebelo
- Laboratory of Cognitive Neuroscience, School of Life Sciences, Neuro-X Institute and Brain Mind Institute, École Polytechnique Fédérale de Lausanne, Lausanne1015, Switzerland
| | - Nicole Young
- Medical Department, SpecialtyCare, Brentwood, TN37027
| | - Francesco Sammartino
- Department of Physical Medicine and Rehabilitation, The Ohio State University, Columbus, OH43210
| | - Catherine Tallon-Baudry
- Laboratoire de Neurosciences Cognitives et Computationnelles, Département d’Etudes Cognitives, École normale supérieure-Paris Sciences et Lettres University, Inserm, Paris75005, France
| | - Vincent Navarro
- Sorbonne Université, Paris Brain Institute—Institut du Cerveau et de la Moelle épinière, Inserm, CNRS, Assistance Publique - Hôpitaux de Paris, Epilepsy Unit, Hôpital de la Pitié-Salpêtrière, Paris75013, France
| | - Ali R. Rezai
- Department of Neurosurgery, Rockefeller Neuroscience Institute—West Virginia University, Morgantown, WV26505
| | - Vibhor Krishna
- Department of Neurosurgery, University of North Carolina at Chapel Hill, Durham, NC27516
| | - Olaf Blanke
- Laboratory of Cognitive Neuroscience, School of Life Sciences, Neuro-X Institute and Brain Mind Institute, École Polytechnique Fédérale de Lausanne, Lausanne1015, Switzerland
- Department of Clinical Neurosciences, University Hospital Geneva, Geneva1205, Switzerland
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2
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Xiao C, Ji YW, Luan YW, Jia T, Yin C, Zhou CY. Differential modulation of subthalamic projection neurons by short-term and long-term electrical stimulation in physiological and parkinsonian conditions. Acta Pharmacol Sin 2022; 43:1928-1939. [PMID: 34880404 PMCID: PMC9343451 DOI: 10.1038/s41401-021-00811-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 10/31/2021] [Indexed: 11/09/2022] Open
Abstract
The subthalamic nucleus (STN) is one of the best targets for therapeutic deep brain stimulation (DBS) to control motor symptoms in Parkinson's disease. However, the precise circuitry underlying the effects of STN-DBS remains unclear. To understand how electrical stimulation affects STN projection neurons, we used a retrograde viral vector (AAV-retro-hSyn-eGFP) to label STN neurons projecting to the substantia nigra pars reticulata (SNr) (STN-SNr neurons) or the globus pallidus interna (GPi) (STN-GPi neurons) in mice, and performed whole-cell patch-clamp recordings from these projection neurons in ex vivo brain slices. We found that STN-SNr neurons exhibited stronger responses to depolarizing stimulation than STN-GPi neurons. In most STN-SNr and STN-GPi neurons, inhibitory synaptic inputs predominated over excitatory inputs and electrical stimulation at 20-130 Hz inhibited these neurons in the short term; its longer-term effects varied. 6-OHDA lesion of the nigrostriatal dopaminergic pathway significantly reduced inhibitory synaptic inputs in STN-GPi neurons, but did not change synaptic inputs in STN-SNr neurons; it enhanced short-term electrical-stimulation-induced inhibition in STN-SNr neurons but reversed the effect of short-term electrical stimulation on the firing rate in STN-GPi neurons from inhibitory to excitatory; in both STN-SNr and STN-GPi neurons, it increased the inhibition but attenuated the enhancement of firing rate induced by long-term electrical stimulation. Our results suggest that STN-SNr and STN-GPi neurons differ in their synaptic inputs, their responses to electrical stimulation, and their modification under parkinsonian conditions; STN-GPi neurons may play important roles in both the pathophysiology and therapeutic treatment of Parkinson's disease.
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Affiliation(s)
- Cheng Xiao
- Jiangsu Province Key Laboratory of Anesthesiology, School of Anesthesiology, Xuzhou Medical University, Xuzhou, 221004, China. .,Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, 221004, China. .,NMPA Key Laboratory for Research and Evaluation of Narcotic and Psychotropic Drugs, School of Anesthesiology, Xuzhou Medical University, Xuzhou, 221004, China.
| | - Ya-wei Ji
- grid.417303.20000 0000 9927 0537Jiangsu Province Key Laboratory of Anesthesiology, School of Anesthesiology, Xuzhou Medical University, Xuzhou, 221004 China
| | - Yi-wen Luan
- grid.417303.20000 0000 9927 0537Jiangsu Province Key Laboratory of Anesthesiology, School of Anesthesiology, Xuzhou Medical University, Xuzhou, 221004 China ,grid.460176.20000 0004 1775 8598Department of Anesthesiology, Wuxi People’s Hospital, Wuxi, 214023 China
| | - Tao Jia
- grid.417303.20000 0000 9927 0537Jiangsu Province Key Laboratory of Anesthesiology, School of Anesthesiology, Xuzhou Medical University, Xuzhou, 221004 China
| | - Cui Yin
- grid.417303.20000 0000 9927 0537Jiangsu Province Key Laboratory of Anesthesiology, School of Anesthesiology, Xuzhou Medical University, Xuzhou, 221004 China ,grid.417303.20000 0000 9927 0537Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, 221004 China ,grid.417303.20000 0000 9927 0537NMPA Key Laboratory for Research and Evaluation of Narcotic and Psychotropic Drugs, School of Anesthesiology, Xuzhou Medical University, Xuzhou, 221004 China
| | - Chun-yi Zhou
- grid.417303.20000 0000 9927 0537Jiangsu Province Key Laboratory of Anesthesiology, School of Anesthesiology, Xuzhou Medical University, Xuzhou, 221004 China ,grid.417303.20000 0000 9927 0537Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, 221004 China ,grid.417303.20000 0000 9927 0537NMPA Key Laboratory for Research and Evaluation of Narcotic and Psychotropic Drugs, School of Anesthesiology, Xuzhou Medical University, Xuzhou, 221004 China
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3
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Milosevic L, Kalia SK, Hodaie M, Lozano AM, Popovic MR, Hutchison WD, Lankarany M. A theoretical framework for the site-specific and frequency-dependent neuronal effects of deep brain stimulation. Brain Stimul 2021; 14:807-821. [PMID: 33991712 DOI: 10.1016/j.brs.2021.04.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 04/01/2021] [Accepted: 04/27/2021] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Deep brain stimulation is an established therapy for several neurological disorders; however, its effects on neuronal activity vary across brain regions and depend on stimulation settings. Understanding these variable responses can aid in the development of physiologically-informed stimulation paradigms in existing or prospective indications. OBJECTIVE Provide experimental and computational insights into the brain-region-specific and frequency-dependent effects of extracellular stimulation on neuronal activity. METHODS In patients with movement disorders, single-neuron recordings were acquired from the subthalamic nucleus, substantia nigra pars reticulata, ventral intermediate nucleus, or reticular thalamus during microstimulation across various frequencies (1-100 Hz) to assess single-pulse and frequency-response functions. Moreover, a biophysically-realistic computational framework was developed which generated postsynaptic responses under the assumption that electrical stimuli simultaneously activated all convergent presynaptic inputs to stimulation target neurons. The framework took into consideration the relative distributions of excitatory/inhibitory afferent inputs to model site-specific responses, which were in turn embedded within a model of short-term synaptic plasticity to account for stimulation frequency-dependence. RESULTS We demonstrated microstimulation-evoked excitatory neuronal responses in thalamic structures (which have predominantly excitatory inputs) and inhibitory responses in basal ganglia structures (predominantly inhibitory inputs); however, higher stimulation frequencies led to a loss of site-specificity and convergence towards neuronal suppression. The model confirmed that site-specific responses could be simulated by accounting for local neuroanatomical/microcircuit properties, while suppression of neuronal activity during high-frequency stimulation was mediated by short-term synaptic depression. CONCLUSIONS Brain-region-specific and frequency-dependant neuronal responses could be simulated by considering neuroanatomical (local microcircuitry) and neurophysiological (short-term plasticity) properties.
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Affiliation(s)
- Luka Milosevic
- Krembil Brain Institute, University Health Network, Toronto, Canada; Institute of Biomedical Engineering, University of Toronto, Toronto, Canada; KITE, Toronto Rehabilitation Institute, University Health Network, Toronto, Canada; CRANIA, University Health Network and University of Toronto, Toronto, Canada.
| | - Suneil K Kalia
- Krembil Brain Institute, University Health Network, Toronto, Canada; KITE, Toronto Rehabilitation Institute, University Health Network, Toronto, Canada; CRANIA, University Health Network and University of Toronto, Toronto, Canada; Division of Neurosurgery, Toronto Western Hospital, University Health Network, Toronto, Canada; Department of Surgery, University of Toronto, Toronto, Canada
| | - Mojgan Hodaie
- Krembil Brain Institute, University Health Network, Toronto, Canada; CRANIA, University Health Network and University of Toronto, Toronto, Canada; Division of Neurosurgery, Toronto Western Hospital, University Health Network, Toronto, Canada; Department of Surgery, University of Toronto, Toronto, Canada
| | - Andres M Lozano
- Krembil Brain Institute, University Health Network, Toronto, Canada; CRANIA, University Health Network and University of Toronto, Toronto, Canada; Division of Neurosurgery, Toronto Western Hospital, University Health Network, Toronto, Canada; Department of Surgery, University of Toronto, Toronto, Canada
| | - Milos R Popovic
- Institute of Biomedical Engineering, University of Toronto, Toronto, Canada; KITE, Toronto Rehabilitation Institute, University Health Network, Toronto, Canada; CRANIA, University Health Network and University of Toronto, Toronto, Canada
| | - William D Hutchison
- CRANIA, University Health Network and University of Toronto, Toronto, Canada; Department of Surgery, University of Toronto, Toronto, Canada; Department of Physiology, University of Toronto, Toronto, Canada
| | - Milad Lankarany
- Krembil Brain Institute, University Health Network, Toronto, Canada; Institute of Biomedical Engineering, University of Toronto, Toronto, Canada; KITE, Toronto Rehabilitation Institute, University Health Network, Toronto, Canada
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4
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Moore C, Xu M, Bohlen JK, Meshul CK. Differential ultrastructural alterations in the Vglut2 glutamatergic input to the substantia nigra pars compacta/pars reticulata following nigrostriatal dopamine loss in a progressive mouse model of Parkinson’s disease. Eur J Neurosci 2020; 53:2061-2077. [DOI: 10.1111/ejn.14894] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 06/26/2020] [Accepted: 06/27/2020] [Indexed: 12/12/2022]
Affiliation(s)
- Cynthia Moore
- Research ServicesVA Medical Center/Portland Portland OR USA
| | - Mo Xu
- Research ServicesVA Medical Center/Portland Portland OR USA
| | | | - Charles K. Meshul
- Research ServicesVA Medical Center/Portland Portland OR USA
- Department of Behavioral Neuroscience and Pathology Oregon Heath & Science University Portland OR USA
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Milosevic L, De Vloo P, Gramer R, Kalia SK, Fasano A, Popovic MR, Hutchison WD. Neuronal Activity and Synaptic Plasticity in a Reimplanted STN-DBS Patient with Parkinson's Disease: Recordings from Two Surgeries. Stereotact Funct Neurosurg 2020; 98:206-212. [PMID: 32294659 DOI: 10.1159/000505705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 12/31/2019] [Indexed: 11/19/2022]
Abstract
The authors report the case of an elderly male in his 60s who, after 5 months of efficacious treatment with chronic deep brain stimulation of the subthalamic nucleus (STN-DBS), developed a hardware-related erosion necessitating removal of the complete DBS system. One and a half years following the first implantation, a new STN-DBS system was implanted along an immediately adjacent trajectory, and reproduction of clinical efficacy was reported. Additionally, 2 microstimulation protocols were compared between the 2 surgeries, i.e., one to assess the stimulation frequency response of STN neurons and another to assess inhibitory synaptic plasticity in the substantia nigra pars reticulata (SNr). The spontaneous neuronal firing rates of STN neurons in each hemisphere were also compared between the 2 surgeries. The results suggest that the frequency-sensitivity of STN neurons may have been reduced (i.e., more resistant to neuronal suppression), while the spontaneous baseline firing rates of STN neurons and the plasticity measured in the SNr remained unchanged (2 factors that may be indicative of neurodegenerative processes).
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Affiliation(s)
- Luka Milosevic
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.,KITE, Toronto Rehabilitation Institute - University Health Network, Toronto, Ontario, Canada.,CRANIA, University Health Network and University of Toronto, Toronto, Ontario, Canada
| | - Philippe De Vloo
- Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Ontario, Canada
| | - Robert Gramer
- Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Ontario, Canada
| | - Suneil K Kalia
- KITE, Toronto Rehabilitation Institute - University Health Network, Toronto, Ontario, Canada.,CRANIA, University Health Network and University of Toronto, Toronto, Ontario, Canada.,Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Ontario, Canada.,Department of Surgery, University of Toronto, Toronto, Ontario, Canada.,Krembil Research Institute - University Health Network, Toronto, Ontario, Canada
| | - Alfonso Fasano
- CRANIA, University Health Network and University of Toronto, Toronto, Ontario, Canada.,Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Ontario, Canada.,Krembil Research Institute - University Health Network, Toronto, Ontario, Canada.,Edmond J. Safra Program in Parkinson's Disease and Morton and Gloria Shulman Movement Disorders Center, Toronto Western Hospital - University Health Network, Toronto, Ontario, Canada.,Division of Neurology, University of Toronto, Toronto, Ontario, Canada
| | - Milos R Popovic
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.,KITE, Toronto Rehabilitation Institute - University Health Network, Toronto, Ontario, Canada.,CRANIA, University Health Network and University of Toronto, Toronto, Ontario, Canada
| | - William D Hutchison
- CRANIA, University Health Network and University of Toronto, Toronto, Ontario, Canada, .,Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Ontario, Canada, .,Department of Surgery, University of Toronto, Toronto, Ontario, Canada, .,Division of Neurology, University of Toronto, Toronto, Ontario, Canada, .,Department of Physiology, University of Toronto, Toronto, Ontario, Canada,
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6
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Milosevic L, Kalia SK, Hodaie M, Lozano AM, Popovic MR, Hutchison WD. Physiological mechanisms of thalamic ventral intermediate nucleus stimulation for tremor suppression. Brain 2019; 141:2142-2155. [PMID: 29878147 PMCID: PMC6022553 DOI: 10.1093/brain/awy139] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 04/05/2018] [Indexed: 11/12/2022] Open
Abstract
Ventral intermediate thalamic deep brain stimulation is a standard therapy for the treatment of medically refractory essential tremor and tremor-dominant Parkinson's disease. Despite the therapeutic benefits, the mechanisms of action are varied and complex, and the pathophysiology and genesis of tremor remain unsubstantiated. This intraoperative study investigated the effects of high frequency microstimulation on both neuronal firing and tremor suppression simultaneously. In each of nine essential tremor and two Parkinson's disease patients who underwent stereotactic neurosurgery, two closely spaced (600 µm) microelectrodes were advanced into the ventral intermediate nucleus. One microelectrode recorded action potential firing while the adjacent electrode delivered stimulation trains at 100 Hz and 200 Hz (2-5 s, 100 µA, 150 µs). A triaxial accelerometer was used to measure postural tremor of the contralateral hand. At 200 Hz, stimulation led to 68 ± 8% (P < 0.001) inhibition of neuronal firing and a 53 ± 5% (P < 0.001) reduction in tremor, while 100 Hz reduced firing by 26 ± 12% (not significant) with a 17 ± 6% (P < 0.05) tremor reduction. The degree of cell inhibition and tremor suppression were significantly correlated (P < 0.001). We also found that the most ventroposterior stimulation sites, closest to the border of the ventral caudal nucleus, had the best effect on tremor. Finally, prior to the inhibition of neuronal firing, microstimulation caused a transient driving of neuronal activity at stimulus onset (61% of sites), which gave rise to a tremor phase reset (73% of these sites). This was likely due to activation of the excitatory glutamatergic cortical and cerebellar afferents to the ventral intermediate nucleus. Temporal characteristics of the driving responses (duration, number of spikes, and onset latency) significantly differed between 100 Hz and 200 Hz stimulation trains. The subsequent inhibition of neuronal activity was likely due to synaptic fatigue. Thalamic neuronal inhibition seems necessary for tremor reduction and may function in effect as a thalamic filter to uncouple thalamo-cortical from cortico-spinal reflex loops. Additionally, our findings shed light on the gating properties of the ventral intermediate nucleus within the cerebello-thalamo-cortical tremor network, provide insight for the optimization of deep brain stimulation technologies, and may inform controlled clinical studies for assessing optimal target locations for the treatment of tremor.
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Affiliation(s)
- Luka Milosevic
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada.,Rehabilitation Engineering Laboratory, Toronto Rehabilitation Institute - University Health Network, Toronto, Canada
| | - Suneil K Kalia
- Department of Surgery, University of Toronto, Toronto, Canada.,Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Canada.,Krembil Research Institute, Toronto, Canada
| | - Mojgan Hodaie
- Department of Surgery, University of Toronto, Toronto, Canada.,Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Canada.,Krembil Research Institute, Toronto, Canada
| | - Andres M Lozano
- Department of Surgery, University of Toronto, Toronto, Canada.,Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, Canada.,Krembil Research Institute, Toronto, Canada
| | - Milos R Popovic
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada.,Rehabilitation Engineering Laboratory, Toronto Rehabilitation Institute - University Health Network, Toronto, Canada
| | - William D Hutchison
- Department of Surgery, University of Toronto, Toronto, Canada.,Krembil Research Institute, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada
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7
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Modulation of inhibitory plasticity in basal ganglia output nuclei of patients with Parkinson's disease. Neurobiol Dis 2019; 124:46-56. [DOI: 10.1016/j.nbd.2018.10.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 10/17/2018] [Accepted: 10/31/2018] [Indexed: 01/07/2023] Open
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Milosevic L, Kalia SK, Hodaie M, Lozano AM, Fasano A, Popovic MR, Hutchison WD. Neuronal inhibition and synaptic plasticity of basal ganglia neurons in Parkinson's disease. Brain 2019; 141:177-190. [PMID: 29236966 PMCID: PMC5917776 DOI: 10.1093/brain/awx296] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 09/20/2017] [Indexed: 12/24/2022] Open
Abstract
Deep brain stimulation of the subthalamic nucleus is an effective treatment for Parkinson’s disease symptoms. The therapeutic benefits of deep brain stimulation are frequency-dependent, but the underlying physiological mechanisms remain unclear. To advance deep brain stimulation therapy an understanding of fundamental mechanisms is critical. The objectives of this study were to (i) compare the frequency-dependent effects on cell firing in subthalamic nucleus and substantia nigra pars reticulata; (ii) quantify frequency-dependent effects on short-term plasticity in substantia nigra pars reticulata; and (iii) investigate effects of continuous long-train high frequency stimulation (comparable to conventional deep brain stimulation) on synaptic plasticity. Two closely spaced (600 µm) microelectrodes were advanced into the subthalamic nucleus (n = 27) and substantia nigra pars reticulata (n = 14) of 22 patients undergoing deep brain stimulation surgery for Parkinson’s disease. Cell firing and evoked field potentials were recorded with one microelectrode during stimulation trains from the adjacent microelectrode across a range of frequencies (1–100 Hz, 100 µA, 0.3 ms, 50–60 pulses). Subthalamic firing attenuated with ≥20 Hz (P < 0.01) stimulation (silenced at 100 Hz), while substantia nigra pars reticulata decreased with ≥3 Hz (P < 0.05) (silenced at 50 Hz). Substantia nigra pars reticulata also exhibited a more prominent increase in transient silent period following stimulation. Patients with longer silent periods after 100 Hz stimulation in the subthalamic nucleus tended to have better clinical outcome after deep brain stimulation. At ≥30 Hz the first evoked field potential of the stimulation train in substantia nigra pars reticulata was potentiated (P < 0.05); however, the average amplitude of the subsequent potentials was rapidly attenuated (P < 0.01). This is suggestive of synaptic facilitation followed by rapid depression. Paired pulse ratios calculated at the beginning of the train revealed that 20 Hz (P < 0.05) was the minimum frequency required to induce synaptic depression. Lastly, the average amplitude of evoked field potentials during 1 Hz pulses showed significant inhibitory synaptic potentiation after long-train high frequency stimulation (P < 0.001) and these increases were coupled with increased durations of neuronal inhibition (P < 0.01). The subthalamic nucleus exhibited a higher frequency threshold for stimulation-induced inhibition than the substantia nigra pars reticulata likely due to differing ratios of GABA:glutamate terminals on the soma and/or the nature of their GABAergic inputs (pallidal versus striatal). We suggest that enhancement of inhibitory synaptic plasticity, and frequency-dependent potentiation and depression are putative mechanisms of deep brain stimulation. Furthermore, we foresee that future closed-loop deep brain stimulation systems (with more frequent off stimulation periods) may benefit from inhibitory synaptic potentiation that occurs after high frequency stimulation.
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Affiliation(s)
- Luka Milosevic
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, Ontario, M5S 3G9, Canada.,Rehabilitation Engineering Laboratory, Toronto Rehabilitation Institute - University Health Network, 520 Sutherland Drive, Toronto, Ontario, M4G 3V9, Canada
| | - Suneil K Kalia
- Department of Surgery, University of Toronto, 149 College Street, 5th Floor, Toronto, Ontario, M5T 1P5, Canada.,Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, 399 Bathurst St, Toronto, Ontario, M5T 2S8, Canada.,Krembil Research Institute, 135 Nassau St, Toronto, Ontario, M5T 1M8, Canada
| | - Mojgan Hodaie
- Department of Surgery, University of Toronto, 149 College Street, 5th Floor, Toronto, Ontario, M5T 1P5, Canada.,Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, 399 Bathurst St, Toronto, Ontario, M5T 2S8, Canada.,Krembil Research Institute, 135 Nassau St, Toronto, Ontario, M5T 1M8, Canada
| | - Andres M Lozano
- Department of Surgery, University of Toronto, 149 College Street, 5th Floor, Toronto, Ontario, M5T 1P5, Canada.,Division of Neurosurgery, Toronto Western Hospital - University Health Network, Toronto, 399 Bathurst St, Toronto, Ontario, M5T 2S8, Canada.,Krembil Research Institute, 135 Nassau St, Toronto, Ontario, M5T 1M8, Canada
| | - Alfonso Fasano
- Krembil Research Institute, 135 Nassau St, Toronto, Ontario, M5T 1M8, Canada.,Morton and Gloria Shulman Movement Disorders Center and the Edmond J. Safra Program in Parkinson's Disease, Toronto Western Hospital - University Health Network, 399 Bathurst St, Toronto, Ontario, M5T 2S8, Canada.,Division of Neurology, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Milos R Popovic
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, Ontario, M5S 3G9, Canada.,Rehabilitation Engineering Laboratory, Toronto Rehabilitation Institute - University Health Network, 520 Sutherland Drive, Toronto, Ontario, M4G 3V9, Canada
| | - William D Hutchison
- Department of Surgery, University of Toronto, 149 College Street, 5th Floor, Toronto, Ontario, M5T 1P5, Canada.,Krembil Research Institute, 135 Nassau St, Toronto, Ontario, M5T 1M8, Canada.,Department of Physiology, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada
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9
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Tiroshi L, Goldberg JA. Population dynamics and entrainment of basal ganglia pacemakers are shaped by their dendritic arbors. PLoS Comput Biol 2019; 15:e1006782. [PMID: 30730886 PMCID: PMC6382172 DOI: 10.1371/journal.pcbi.1006782] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 02/20/2019] [Accepted: 01/10/2019] [Indexed: 11/30/2022] Open
Abstract
The theory of phase oscillators is an essential tool for understanding population dynamics of pacemaking neurons. GABAergic pacemakers in the substantia nigra pars reticulata (SNr), a main basal ganglia (BG) output nucleus, receive inputs from the direct and indirect pathways at distal and proximal regions of their dendritic arbors, respectively. We combine theory, optogenetic stimulation and electrophysiological experiments in acute brain slices to ask how dendritic properties impact the propensity of the various inputs, arriving at different locations along the dendrite, to recruit or entrain SNr pacemakers. By combining cable theory with sinusoidally-modulated optogenetic activation of either proximal somatodendritic regions or the entire somatodendritic arbor of SNr neurons, we construct an analytical model that accurately fits the empirically measured somatic current response to inputs arising from illuminating the soma and various portions of the dendritic field. We show that the extent of the dendritic tree that is illuminated generates measurable and systematic differences in the pacemaker’s phase response curve (PRC), causing a shift in its peak. Finally, we show that the divergent PRCs correctly predict differences in two major features of the collective dynamics of SNr neurons: the fidelity of population responses to sudden step-like changes in inputs; and the phase latency at which SNr neurons are entrained by rhythmic stimulation, which can occur in the BG under both physiological and pathophysiological conditions. Our novel method generates measurable and physiologically meaningful spatial effects, and provides the first empirical demonstration of how the collective responses of SNr pacemakers are determined by the transmission properties of their dendrites. SNr dendrites may serve to delay distal striatal inputs so that they impinge on the spike initiation zone simultaneously with pallidal and subthalamic inputs in order to guarantee a fair competition between the influence of the monosynaptic direct- and polysynaptic indirect pathways. The substantia nigra pars reticulata (SNr) is a main output nucleus of the basal ganglia (BG), where inputs from the competing direct and indirect pathways converge onto the same neurons. Interestingly, these inputs are differentially distributed with direct and indirect pathway projections arriving at distal and proximal regions of the dendritic arbor, respectively. We employ a novel method combining theory with electrophysiological experiments and optogenetics to study the distinct effects of inputs arriving at different locations along the dendrite. Our approach represents a useful compromise between complexity and reduction in modelling. Our work addresses the question of high fidelity encoding of inputs by networks of neurons in the new context of pacemaking neurons, which are driven to fire by their intrinsic dynamics rather than by a network state. We provide the first empirical demonstration that dendritic delays can introduce latencies in the responses of a population of neurons that are commensurate with synaptic delays, suggesting a new role for SNr dendrites with implications for BG function.
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Affiliation(s)
- Lior Tiroshi
- Department of Medical Neurobiology, Institute of Medical Research Israel–Canada, The Faculty of Medicine, Jerusalem, Israel
- Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Joshua A. Goldberg
- Department of Medical Neurobiology, Institute of Medical Research Israel–Canada, The Faculty of Medicine, Jerusalem, Israel
- * E-mail:
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Abstract
Basal ganglia interact in a complex way which is still not completely understood. The model generally used to explain basal ganglia interactions is based on experimental data in animals, but its validation in humans has been hampered by methodological restrictions. The time-relationship (partial correlation) of the fluctuations of the blood-oxygen-level-dependent signals recorded in the main basal ganglia was used here (32 healthy volunteers; 18-72 years of age; 16 males and 16 females) to test whether the interaction of the main basal ganglia in humans follows the pattern of functional connectivity in animals. Data showed that most basal ganglia have a functional connectivity which is compatible with that of the established closed-loop model. The strength of the connectivity of some basal ganglia changed with finger motion, suggesting that the functional interactions between basal ganglia are quickly restructured by the motor tasks. The present study with the motor cortico-BG loop centers supports the circling dynamic of the basal ganglia model in humans, showing that motor tasks may change the functional connectivity of these centers.
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11
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Çavdar S, Özgür M, Çakmak YÖ, Kuvvet Y, Kunt SK, Sağlam G. Afferent projections of the subthalamic nucleus in the rat: emphasis on bilateral and interhemispheric connections. Acta Neurobiol Exp (Wars) 2018. [DOI: 10.21307/ane-2018-023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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12
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Gouty-Colomer LA, Michel FJ, Baude A, Lopez-Pauchet C, Dufour A, Cossart R, Hammond C. Mouse subthalamic nucleus neurons with local axon collaterals. J Comp Neurol 2017; 526:275-284. [DOI: 10.1002/cne.24334] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 09/08/2017] [Accepted: 09/10/2017] [Indexed: 11/08/2022]
Affiliation(s)
- Laurie-Anne Gouty-Colomer
- INSERM U901; Marseille France
- Aix-Marseille University, UMR 901; Marseille France
- INMED; Marseille France
| | - François J Michel
- INSERM U901; Marseille France
- Aix-Marseille University, UMR 901; Marseille France
- INMED; Marseille France
| | - Agnès Baude
- INSERM U901; Marseille France
- Aix-Marseille University, UMR 901; Marseille France
- INMED; Marseille France
| | - Catherine Lopez-Pauchet
- INSERM U901; Marseille France
- Aix-Marseille University, UMR 901; Marseille France
- INMED; Marseille France
| | | | - Rosa Cossart
- INSERM U901; Marseille France
- Aix-Marseille University, UMR 901; Marseille France
- INMED; Marseille France
| | - Constance Hammond
- INSERM U901; Marseille France
- Aix-Marseille University, UMR 901; Marseille France
- INMED; Marseille France
- B&A Therapeutics, INMED; Marseille France
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13
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Pearlstein E, Gouty-Colomer LA, Michel FJ, Cloarec R, Hammond C. Glutamatergic synaptic currents of nigral dopaminergic neurons follow a postnatal developmental sequence. Front Cell Neurosci 2015; 9:210. [PMID: 26074777 PMCID: PMC4448554 DOI: 10.3389/fncel.2015.00210] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 05/15/2015] [Indexed: 01/20/2023] Open
Abstract
The spontaneous activity pattern of adult dopaminergic (DA) neurons of the substantia nigra pars compacta (SNc) results from interactions between intrinsic membrane conductances and afferent inputs. In adult SNc DA neurons, low-frequency tonic background activity is generated by intrinsic pacemaker mechanisms, whereas burst generation depends on intact synaptic inputs in particular the glutamatergic ones. Tonic DA release in the striatum during pacemaking is required to maintain motor activity, and burst firing evokes phasic DA release, necessary for cue-dependent learning tasks. However, it is still unknown how the firing properties of SNc DA neurons mature during postnatal development before reaching the adult state. We studied the postnatal developmental profile of spontaneous and evoked AMPA and NMDA (N-Methyl-D-aspartic acid) receptor-mediated excitatory postsynaptic currents (EPSCs) in SNc DA neurons in brain slices from immature (postnatal days P4–P10) and young adult (P30–P50) tyrosine hydroxylase (TH)-green fluorescent protein mice. We found that somato-dendritic fields of SNc DA neurons are already mature at P4–P10. In contrast, spontaneous glutamatergic EPSCs show a developmental sequence. Spontaneous NMDA EPSCs in particular are larger and more frequent in immature SNc DA neurons than in young adult ones and have a bursty pattern. They are mediated by GluN2B and GluN2D subunit-containing NMDA receptors. The latter generate long-lasting, DQP 1105-sensitive, spontaneous EPSCs, which are transiently recorded during this early period. Due to high NMDA activity, immature SNc DA neurons generate large and long lasting NMDA receptor-dependent (APV-sensitive) bursts in response to the stimulation of the subthalamic nucleus. We conclude that the transient high NMDA activity allows calcium influx into the dendrites of developing SNc DA neurons.
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Affiliation(s)
- Edouard Pearlstein
- UMR 901, Aix-Marseille Université Marseille, France ; Institut de Neurobiologie de la Méditerranée, Inserm UMR 901 Marseille, France
| | - Laurie-Anne Gouty-Colomer
- UMR 901, Aix-Marseille Université Marseille, France ; Institut de Neurobiologie de la Méditerranée, Inserm UMR 901 Marseille, France
| | - François J Michel
- UMR 901, Aix-Marseille Université Marseille, France ; Institut de Neurobiologie de la Méditerranée, Inserm UMR 901 Marseille, France
| | - Robin Cloarec
- UMR 901, Aix-Marseille Université Marseille, France ; Institut de Neurobiologie de la Méditerranée, Inserm UMR 901 Marseille, France
| | - Constance Hammond
- UMR 901, Aix-Marseille Université Marseille, France ; Institut de Neurobiologie de la Méditerranée, Inserm UMR 901 Marseille, France
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14
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Subthalamotomy-induced changes in dopamine receptors in parkinsonian monkeys. Exp Neurol 2014; 261:816-25. [DOI: 10.1016/j.expneurol.2014.08.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 08/11/2014] [Accepted: 08/16/2014] [Indexed: 11/17/2022]
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15
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Striatal interaction among dopamine, glutamate and ascorbate. Neuropharmacology 2012; 63:1308-14. [DOI: 10.1016/j.neuropharm.2012.08.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 07/24/2012] [Accepted: 08/13/2012] [Indexed: 11/23/2022]
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16
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Aristieta A, Azkona G, Sagarduy A, Miguelez C, Ruiz-Ortega JÁ, Sanchez-Pernaute R, Ugedo L. The role of the subthalamic nucleus in L-DOPA induced dyskinesia in 6-hydroxydopamine lesioned rats. PLoS One 2012; 7:e42652. [PMID: 22880070 PMCID: PMC3412805 DOI: 10.1371/journal.pone.0042652] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 07/09/2012] [Indexed: 01/25/2023] Open
Abstract
L-DOPA is the most effective treatment for Parkinson's disease (PD), but prolonged use leads to disabling motor complications including dyskinesia. Strong evidence supports a role of the subthalamic nucleus (STN) in the pathophysiology of PD whereas its role in dyskinesia is a matter of controversy. Here, we investigated the involvement of STN in dyskinesia, using single-unit extracellular recording, behavioural and molecular approaches in hemi-parkinsonian rats rendered dyskinetic by chronic L-DOPA administration. Our results show that chronic L-DOPA treatment does not modify the abnormal STN activity induced by the 6-hydroxydopamine lesion of the nigrostriatal pathway in this model. Likewise, we observed a loss of STN responsiveness to a single L-DOPA dose both in lesioned and sham animals that received daily L-DOPA treatment. We did not find any correlation between the abnormal involuntary movement (AIM) scores and the electrophysiological parameters of STN neurons recorded 24 h or 20–120 min after the last L-DOPA injection, except for the axial subscores. Nonetheless, unilateral chemical ablation of the STN with ibotenic acid resulted in a reduction in global AIM scores and peak-severity of dyskinesia. In addition, STN lesion decreased the anti-dyskinetogenic effect of buspirone in a reciprocal manner. Striatal protein expression was altered in dyskinetic animals with increases in ΔFosB, phosphoDARPP-32, dopamine receptor (DR) D3 and DRD2/DRD1 ratio. The STN lesion attenuated the striatal molecular changes and normalized the DRD2/DRD1 ratio. Taken together, our results show that the STN plays a role, if modest, in the physiopathology of dyskinesias.
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Affiliation(s)
- Asier Aristieta
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, Leioa, Spain
| | - Garikoitz Azkona
- Laboratory of Stem Cells and Neural Repair, Fundacion Inbiomed, San Sebastian, Spain
| | - Ainhoa Sagarduy
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, Leioa, Spain
| | - Cristina Miguelez
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, Leioa, Spain
| | - José Ángel Ruiz-Ortega
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, Leioa, Spain
| | - Rosario Sanchez-Pernaute
- Laboratory of Stem Cells and Neural Repair, Fundacion Inbiomed, San Sebastian, Spain
- * E-mail: (RSP); (LU)
| | - Luisa Ugedo
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, Leioa, Spain
- * E-mail: (RSP); (LU)
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17
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Morales M, Pickel VM. Insights to drug addiction derived from ultrastructural views of the mesocorticolimbic system. Ann N Y Acad Sci 2011; 1248:71-88. [PMID: 22171551 DOI: 10.1111/j.1749-6632.2011.06299.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Drugs of abuse increase the release of dopamine from mesocorticolimbic neurons in the ventral tegmental area. Thus, insights into the cytoarchitecture and the synaptic circuitry affecting the activity of dopaminergic neurons in this area are fundamental for understanding the commonalities produced by mechanistically distinct drugs of abuse. Electron microscopic immunolabeling has provided these insights and also shown the critical relationships between the dopaminergic axon terminals and their targeted neurons in the prefrontal cortex and in the both the dorsal and ventral striatum. These brain regions are among those where dopamine and associated neurotransmitters are most implicated in the transition from recreational to compulsive consumption of reinforcing drugs. Thus, the synaptic circuitry and drug-induced plasticity occurring in the ventral tegmental area and in dopamine-targeted regions are reviewed, as both are essential for understanding the long-lasting changes produced by addictive substances.
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Affiliation(s)
- Marisela Morales
- National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, USA.
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Naskar S, Sood SK, Goyal V, Dhara M. RETRACTED: Mechanism(s) of deep brain stimulation and insights into cognitive outcomes in Parkinson's disease. ACTA ACUST UNITED AC 2010; 65:1-13. [DOI: 10.1016/j.brainresrev.2010.04.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 04/12/2010] [Accepted: 04/27/2010] [Indexed: 11/30/2022]
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19
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Lee CR, Tepper JM. Basal ganglia control of substantia nigra dopaminergic neurons. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 2010:71-90. [PMID: 20411769 DOI: 10.1007/978-3-211-92660-4_6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/27/2023]
Abstract
Although substantia nigra dopaminergic neurons are spontaneously active both in vivo and in vitro, this activity does not depend on afferent input as these neurons express an endogenous calcium-dependent oscillatory mechanism sufficient to drive action potential generation. However, afferents to these neurons, a large proportion of them GABAergic and arising from other nuclei in the basal ganglia, play a crucial role in modulating the activity of dopaminergic neurons. In the absence of afferent activity or when in brain slices, dopaminergic neurons fire in a very regular, pacemaker-like mode. Phasic activity in GABAergic, glutamatergic, and cholinergic inputs modulates the pacemaker activity into two other modes. The most common is a random firing pattern in which interspike intervals assume a Poisson-like distribution, and a less common pattern, often in response to a conditioned stimulus or a reward in which the neurons fire bursts of 2-8 spikes time-locked to the stimulus. Typically in vivo, all three firing patterns are observed, intermixed, in single nigrostriatal neurons varying over time. Although the precise mechanism(s) underlying the burst are currently the focus of intensive study, it is obvious that bursting must be triggered by afferent inputs. Most of the afferents to substantia nigra pars compacta dopaminergic neurons comprise monosynaptic inputs from GABAergic projection neurons in the ipsilateral neostriatum, the globus pallidus, and the substantia nigra pars reticulata. A smaller fraction of the basal ganglia inputs, something less than 30%, are glutamatergic and arise principally from the ipsilateral subthalamic nucleus and pedunculopontine nucleus. The pedunculopontine nucleus also sends a cholinergic input to nigral dopaminergic neurons. The GABAergic pars reticulata projection neurons also receive inputs from all of these sources, in some cases relaying them disynaptically to the dopaminergic neurons, thereby playing a particularly significant role in setting and/or modulating the firing pattern of the nigrostriatal neurons.
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Affiliation(s)
- Christian R Lee
- Department of Neurosurgery, New York University School of Medicine, 4 New York, NY 10016, USA.
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Lateral hypothalamic orexin/hypocretin neurons: A role in reward-seeking and addiction. Brain Res 2009; 1314:74-90. [PMID: 19815001 DOI: 10.1016/j.brainres.2009.09.106] [Citation(s) in RCA: 288] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Revised: 09/27/2009] [Accepted: 09/29/2009] [Indexed: 12/30/2022]
Abstract
Orexins (synonymous with hypocretins) are recently discovered neuropeptides made exclusively in hypothalamus. Behavioral, anatomical, and neurophysiological studies show that a subset of these cells, specifically those in lateral hypothalamus (LH), are involved in reward processing and addictive behaviors. Fos expression in LH orexin neurons varied in proportion to conditioned place preference (CPP) for morphine, cocaine, or food. This relationship occurred both in drug-naïve rats and in animals during protracted morphine withdrawal, when drug preference was elevated but food preference was decreased. Inputs to the LH orexin cell field from lateral septum and bed nucleus of the stria terminalis were Fos-activated during cocaine CPP in proportion to the preference expressed in each animal. This implies that these inputs may be involved in driving the conditioned responses in LH orexin neurons. Related studies showed that LH orexin neurons that project to ventral tegmental area (VTA) had greater Fos induction in association with elevated morphine preference during protracted withdrawal than non-VTA-projecting orexin neurons, indicating that the VTA is an important site of action for orexin's role in reward processing. In addition, stimulation of LH orexin neurons, or microinjection of orexin into VTA, reinstated an extinguished morphine preference. In self-administration studies, the orexin 1 receptor antagonist SB-334867 (SB) blocked cocaine-seeking induced by discrete or contextual cues previously associated with cocaine, but not by a priming injection of cocaine. There was no effect of SB on cocaine self-administration itself, indicating that it did not interfere with the drug's reinforcing properties. Neurophysiological studies revealed that locally applied orexin often augmented responses of VTA dopamine (DA) neurons to activation of the medial prefrontal cortex (mPFC), consistent with the view that orexin facilitates activation of VTA DA neurons by stimulus-reward associations. This LH-to-VTA orexin pathway was found to be necessary for learning a morphine place preference. These findings are consistent with results showing that orexin facilitates glutamate-mediated responses, and is necessary for glutamate-dependent long-term potentiation in VTA DA neurons. We surmise from these studies that LH orexin neurons play an important role in reward processing and addiction and that LH orexin cells are an important input to VTA for behavioral effects associated with reward-paired stimuli.
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Moráles I, Fuentes A, Gonzalez-Hernandez T, Rodríguez M. Osmosensitive response of glutamate in the substantia nigra. Exp Neurol 2009; 220:335-40. [PMID: 19766632 DOI: 10.1016/j.expneurol.2009.09.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 09/09/2009] [Accepted: 09/11/2009] [Indexed: 11/18/2022]
Abstract
Previous studies have suggested the increase of extracellular glutamate (GLU) in the substantia nigra (SN) as a cause of dopamine-cell degeneration (excitotoxicity) in Parkinson's disease (PD). However, the mechanisms involved in this increase remain unknown. The present work studied osmoregulation as a cause of GLU release in the SN. Microdialysis was used to change extracellular osmolarity, to administer drugs and to quantify the extracellular non-synaptic GLU (EnS-GLU). Two osmolarity modifications were performed, a moderate decrease (5%) resembling physiological modifications and a substantial decrease (>or=20% decrease) similar to that observed under pathological conditions. Hypo-osmolarity induced a dose-response (285-80 mOsm) increase of EnS-GLU which was detected after small osmolarity modifications (15 mOsm) and which was very marked (>1000%) after more intense osmolarity changes. This response disappeared after pre-treating rats with a P2 purinergic-receptor antagonist (pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid; 1 mM) suggesting ATP involvement in the osmosensitive EnS-GLU response. The EnS-GLU increase observed after administration of ATP (0.1-100 microM) and 2-methylthioadenosine triphosphate tetrasodium (P2-receptor agonist; 100 microM) and the lack of effects of adenosine administration (1 mM) suggest that the ATP action on P2 receptors is an amplificatory mechanism in the osmosensitive EnS-GLU response. The marked action of osmolarity on extracellular Glu suggests osmolarity regulation as a possible source for excitotoxicity in the SN.
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Affiliation(s)
- Ingrid Moráles
- Laboratory of Neurobiology and Experimental Neurology, Department of Physiology Faculty of Medicine, University of La Laguna, La Laguna, Tenerife, Canary Islands, Spain
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22
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Mobilization of calcium from intracellular stores facilitates somatodendritic dopamine release. J Neurosci 2009; 29:6568-79. [PMID: 19458227 DOI: 10.1523/jneurosci.0181-09.2009] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Somatodendritic dopamine (DA) release in the substantia nigra pars compacta (SNc) shows a limited dependence on extracellular calcium concentration ([Ca(2+)](o)), suggesting the involvement of intracellular Ca(2+) stores. Here, using immunocytochemistry we demonstrate the presence of the sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase 2 (SERCA2) that sequesters cytosolic Ca(2+) into the endoplasmic reticulum (ER), as well as inositol 1,4,5-triphosphate receptors (IP(3)Rs) and ryanodine receptors (RyRs) in DAergic neurons. Notably, RyRs were clustered at the plasma membrane, poised for activation by Ca(2+) entry. Using fast-scan cyclic voltammetry to monitor evoked extracellular DA concentration ([DA](o)) in midbrain slices, we found that SERCA inhibition by cyclopiazonic acid (CPA) decreased evoked [DA](o) in the SNc, indicating a functional role for ER Ca(2+) stores in somatodendritic DA release. Implicating IP(3)R-dependent stores, an IP(3)R antagonist, 2-APB, also decreased evoked [DA](o). Moreover, DHPG, an agonist of group I metabotropic glutamate receptors (mGluR1s, which couple to IP(3) production), increased somatodendritic DA release, whereas CPCCOEt, an mGluR1 antagonist, suppressed it. Release suppression by mGluR1 blockade was prevented by 2-APB or CPA, indicating facilitation of DA release by endogenous glutamate acting via mGluR1s and IP(3)R-gated Ca(2+) stores. Similarly, activation of RyRs by caffeine increased [Ca(2+)](i) and elevated evoked [DA](o). The increase in DA release was prevented by a RyR blocker, dantrolene, and by CPA. Importantly, the efficacy of dantrolene was enhanced in low [Ca(2+)](o), suggesting a mechanism for maintenance of somatodendritic DA release with limited Ca(2+) entry. Thus, both mGluR1-linked IP(3)R- and RyR-dependent ER Ca(2+) stores facilitate somatodendritic DA release in the SNc.
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Paraquat inhibits postsynaptic AMPA receptors on dopaminergic neurons in the substantia nigra pars compacta. Biochem Pharmacol 2008; 76:1155-64. [DOI: 10.1016/j.bcp.2008.08.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 08/05/2008] [Accepted: 08/05/2008] [Indexed: 11/27/2022]
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Aston-Jones G, Smith RJ, Moorman DE, Richardson KA. Role of lateral hypothalamic orexin neurons in reward processing and addiction. Neuropharmacology 2008; 56 Suppl 1:112-21. [PMID: 18655797 DOI: 10.1016/j.neuropharm.2008.06.060] [Citation(s) in RCA: 195] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 06/06/2008] [Accepted: 06/12/2008] [Indexed: 10/21/2022]
Abstract
Orexins (also known as hypocretins) are recently discovered neuropeptides made exclusively in hypothalamic neurons that have been shown to be important in narcolepsy/cataplexy and arousal. Here, we conducted behavioral, anatomical and neurophysiological studies that show that a subset of these cells, located specifically in lateral hypothalamus (LH), are involved in reward processing and addictive behaviors. We found that Fos expression in LH orexin neurons varied in proportion to preference for morphine, cocaine or food. This relationship obtained both in drug naïve rats and in animals during protracted morphine withdrawal, when drug preference was elevated but food preference was decreased. Recent studies showed that LH orexin neurons that project to ventral tegmental area (VTA) have greater Fos induction in association with elevated morphine preference during protracted withdrawal than non-VTA-projecting orexin neurons, indicating that the VTA is an important site of action for orexin's role in reward processing. In addition, we found that stimulation of LH orexin neurons, or microinjection of orexin into VTA, reinstated an extinguished morphine preference. Most recently, using a self-administration paradigm we discovered that the Ox1 receptor antagonist SB-334867 (SB) blocks cocaine-seeking induced by discrete or contextual cues, but not by a priming injection of cocaine. Neurophysiological studies revealed that locally applied orexin often augmented responses of VTA dopamine (DA) neurons to activation of the medial prefrontal cortex (mPFC), consistent with the view that orexin facilitates activation of VTA DA neurons by stimulus-reward associations. We also recently showed that orexin in VTA is necessary for learning a morphine place preference. These findings are consistent with results from others showing that orexin facilitates glutamate-mediated responses, and is necessary for glutamate-dependent long-term potentiation, in VTA DA neurons. We surmise from these studies that LH orexin neurons play an important role in reward processing and addiction, and that LH orexin cells are an important input to VTA for behavioral effects associated with reward-paired stimuli.
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Affiliation(s)
- Gary Aston-Jones
- Department of Neurosciences, Medical University of South Carolina, Basic Science Building 403, 173 Ashley Avenue, MSC 510, Charleston, SC 29425-5100, USA.
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25
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Xin T, Ai Y, Gerhardt G, Gash D, Zhang Z. Globus pallidus plays a critical role in neurotrophic factor induced functional improvements in hemiparkinsonian monkeys. Biochem Biophys Res Commun 2008; 370:434-9. [PMID: 18381061 DOI: 10.1016/j.bbrc.2008.03.108] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Accepted: 03/20/2008] [Indexed: 11/18/2022]
Abstract
This study was designed to test the hypothesis that the integrity of the globus pallidus (GP) is critical for neurotrophic factor, such as glial-derived neurotrophic factor (GDNF), induced functional changes in rhesus macaques with MPTP-induced parkinsonism, because our previous studies demonstrated that the GP was one of the most affected areas as assessed by the levels of dopamine (DA) and its metabolites. A group of eight hemiparkinsonian monkeys with pallidal lesions, which positively responsed to intraventricular (ICV) injections of GDNF prior to the lesions, and a group of eight hemiparkinsonian monkeys without pallidal lesions, were treated with GDNF after a long washout period after the initial ICV infusions of GDNF. Significant behavioral improvements were only seen in the monkeys without pallidal lesions that received GDNF. Monkeys with pallidal lesions failed to exhibit any behavioral improvement even though they had elevated nigral DA levels. The results suggest that the GP is critical for neurotrophic factor induced functional changes in PD monkeys.
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Affiliation(s)
- Tao Xin
- Department of Neurosurgery, Shandong Provincial Hospital, Shandong, University School of Medicine, Jinan, Shandong 250021, PR China
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26
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Morera-Herreras T, Ruiz-Ortega J, Gómez-Urquijo S, Ugedo L. Involvement of subthalamic nucleus in the stimulatory effect of Δ9-tetrahydrocannabinol on dopaminergic neurons. Neuroscience 2008; 151:817-23. [DOI: 10.1016/j.neuroscience.2007.11.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Revised: 10/22/2007] [Accepted: 11/19/2007] [Indexed: 11/26/2022]
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An fMRI Study of Frontal–Subcortical Skeletomotor Circuit and Dorsolateral Prefrontal Cortex Function Using a Paced Motor Activation Paradigm. Brain Imaging Behav 2007. [DOI: 10.1007/s11682-007-9006-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Abstract
The ventral tegmental area (VTA) is thought to play an important role in reward function. Two populations of neurons, containing either dopamine (DA) or gamma-amino butyric acid (GABA), have been extensively characterized in this area. However, recent electrophysiological studies are consistent with the notion that neurons that utilize neurotransmitters other than DA or GABA are likely to be present in the VTA. Given the pronounced phenotypic diversity of neurons in this region, we have proposed that additional cell types, such as those that express the neurotransmitter glutamate may also be present in this area. Thus, by using in situ hybridization histochemistry we investigated whether transcripts encoded by genes for the two vesicular glutamate transporters, VGluT1 or VGluT2, were expressed in the VTA. We found that VGluT2 mRNA but not VGluT1 mRNA is expressed in the VTA. Neurons expressing VGluT2 mRNA were differentially distributed throughout the rostro-caudal and medio-lateral aspects of the VTA, with the highest concentration detected in rostro-medial areas. Phenotypic characterization with double in situ hybridization of these neurons indicated that they rarely co-expressed mRNAs for tyrosine hydroxylase (TH, marker for DAergic neurons) or glutamic acid decarboxylase (GAD, marker for GABAergic neurons). Based on the results described here, we concluded that the VTA contains glutamatergic neurons that in their vast majority are clearly non-DAergic and non-GABAergic.
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Affiliation(s)
- Tsuyoshi Yamaguchi
- National Institute on Drug Abuse, Cellular Neurophysiology, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA
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Florio T, Scarnati E, Confalone G, Minchella D, Galati S, Stanzione P, Stefani A, Mazzone P. High-frequency stimulation of the subthalamic nucleus modulates the activity of pedunculopontine neurons through direct activation of excitatory fibres as well as through indirect activation of inhibitory pallidal fibres in the rat. Eur J Neurosci 2007; 25:1174-86. [PMID: 17331213 DOI: 10.1111/j.1460-9568.2007.05360.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Recent data suggest a potential role of pedunculopontine nucleus (PPN) electrical stimulation in improving gait and posture in Parkinson's disease. Because the PPN receives fibres from the subthalamic nucleus (STN), we investigated the effects of STN-high-frequency stimulation (HFS) on PPN neuronal activity in intact rats and in rats bearing either an ibotenate lesion of the entopeduncular nucleus (EP) or a lesion of the substantia nigra (SN). The main response of PPN neurons to STN single-shock stimulations in the three experimental groups was a short latency (4.5 +/- 2.1 ms) and brief (15.3 +/- 6.5 ms) excitation. This response was maintained during 1-5 s of STN-HFS (130 Hz, 60 micros, 100-1000 microA). In EP-lesioned rats the percentage (75.0%) of PPN neurons showing a modulation of activity following STN-HFS was significantly higher compared with that observed in intact (39.7%) and in SN-lesioned rats (35.4%). Furthermore, in EP-lesioned rats the most frequent response of PPN neurons following STN-HFS was a 5-20 s excitation, which was present in 76.6% of responsive neurons in comparison to 15.4% and 9.1% of neurons responsive in intact and in 6-hydroxydopamine-lesioned rats, respectively. Neurons responsive to STN-HFS in the three experimental groups showed either a sharp positively skewed distribution of interspike intervals or multisecond oscillations in autocorrelograms. The results support that STN-HFS modulates the PPN through a balance of excitatory and inhibitory influences, which may be independent from the dopaminergic nigral neurons. In the absence of inhibitory EP fibres, the direct excitatory influence exerted by the STN on the PPN appears to predominate.
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Affiliation(s)
- Tiziana Florio
- Department of Sciences and Biomedical Technologies, University of L'Aquila, L'Aquila, Italy
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Deniau JM, Mailly P, Maurice N, Charpier S. The pars reticulata of the substantia nigra: a window to basal ganglia output. PROGRESS IN BRAIN RESEARCH 2007; 160:151-72. [PMID: 17499113 DOI: 10.1016/s0079-6123(06)60009-5] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Together with the internal segment of the globus pallidus (GP(i)), the pars reticulata of the substantia nigra (SNr) provides a main output nucleus of the basal ganglia (BG) where the final stage of information processing within this system takes place. In the last decade, progress on the anatomical organization and functional properties of BG output neurons have shed some light on the mechanisms of integration taking place in these nuclei and leading to normal and pathological BG outflow. In this review focused on the SNr, after describing how the anatomical arrangement of nigral cells and their afferents determines specific input-output registers, we examine how the basic electrophysiological properties of the cells and their interaction with synaptic inputs contribute to the spatio-temporal shaping of BG output. The reported data show that the intrinsic membrane properties of the neurons subserves a tonic discharge allowing BG to gate the transmission of information to motor and cognitive systems thereby contributing to appropriate selection of behavior.
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Affiliation(s)
- J M Deniau
- Dynamique et Physiopathologie des Réseaux Neuronaux, INSERM U667, UPMC, Collège de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.
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31
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Martín-Ibañez R, Jenstad M, Berghuis P, Edwards RH, Hioki H, Kaneko T, Mulder J, Canals JM, Ernfors P, Chaudhry FA, Harkany T. Vesicular glutamate transporter 3 (VGLUT3) identifies spatially segregated excitatory terminals in the rat substantia nigra. Eur J Neurosci 2006; 23:1063-70. [PMID: 16519671 DOI: 10.1111/j.1460-9568.2006.04601.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The excitability of dopaminergic (DA) neurons in the substantia nigra is controlled by the convergent activity of multiple glutamatergic afferents. Here, we show that vesicular glutamate transporter 3 (VGLUT3)-immunoreactive (ir) terminals segregate to the perisomatic region of DA neurons in the substantia nigra pars compacta, and VGLUT3 decorates a synapse population distinct from those marked by vesicular glutamate transporters 1 and 2. VGLUT3-ir nerve endings form asymmetric terminals on DA neurons. Retrograde tracing suggests the superior colliculus as an origin of excitatory VGLUT3-ir afferents. Collectively, our data indicate that VGLUT3 identifies a novel excitatory terminal subset that contributes to the tuning of DA cell excitability in the substantia nigra.
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Affiliation(s)
- Raquel Martín-Ibañez
- Laboratory for Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Scheeles väg 1:A1
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Abstract
Deep brain stimulation (DBS) has provided remarkable benefits for people with a variety of neurologic conditions. Stimulation of the ventral intermediate nucleus of the thalamus can dramatically relieve tremor associated with essential tremor or Parkinson disease (PD). Similarly, stimulation of the subthalamic nucleus or the internal segment of the globus pallidus can substantially reduce bradykinesia, rigidity, tremor, and gait difficulties in people with PD. Multiple groups are attempting to extend this mode of treatment to other conditions. Yet, the precise mechanism of action of DBS remains uncertain. Such studies have importance that extends beyond clinical therapeutics. Investigations of the mechanisms of action of DBS have the potential to clarify fundamental issues such as the functional anatomy of selected brain circuits and the relationship between activity in those circuits and behavior. Although we review relevant clinical issues, we emphasize the importance of current and future investigations on these topics.
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Affiliation(s)
- Joel S. Perlmutter
- Departments of Neurology, Radiology, Physical Therapy and Anatomy & Neurobiology, Washington University School of Medicine, Washington University in St. Louis, St. Louis, Missouri 63110
| | - Jonathan W. Mink
- Departments of Neurology, Neurobiology & Anatomy, Brain & Cognitive Sciences, and Pediatrics, University of Rochester, Rochester, New York 14642
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Shigenaga Y, Moritani M, Oh SJ, Park KP, Paik SK, Bae JY, Kim HN, Ma SK, Park CW, Yoshida A, Ottersen OP, Bae YC. The distribution of inhibitory and excitatory synapses on single, reconstructed jaw-opening motoneurons in the cat. Neuroscience 2005; 133:507-18. [PMID: 15878646 DOI: 10.1016/j.neuroscience.2005.02.022] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Revised: 02/03/2005] [Accepted: 02/12/2005] [Indexed: 11/21/2022]
Abstract
In a previous study, we reported that the distribution of inhibitory input, in contrast to excitatory input, decreased somatofugally along dendrites of cat jaw-closing alpha-motoneurons [J Comp Neurol 414 (1999) 454]. The present study examined the distribution of GABA, glycine, and glutamate immunopositive boutons covering horseradish peroxidase-labeled cat jaw-opening motoneurons. The motoneurons were divided into four compartments: the soma, and primary, intermediate, and distal dendrites. Ninety-seven percent of the total number of studied boutons had immunoreactivity for at least one of the three amino acids. The proportion of boutons immunoreactive for GABA and/or glycine was lower than the proportion of boutons immunoreactive for glutamate. Boutons immunoreactive to glycine alone were more numerous than boutons double-labeled for GABA and glycine, which, in turn, occurred more frequently than boutons immunoreactive to GABA alone. The percentage synaptic covering (proportion of membrane covered by synaptic boutons) of the putatively excitatory (glutamate containing) and putatively inhibitory (GABA and/or glycine containing) boutons decreased somatofugally along the dendrites. Such systematic variations were not seen in the packing density (number of boutons per 100 microm(2)); the packing density showed a distinct drop between the soma and primary dendrites but did not differ significantly among the three dendritic compartments. Overall, the packing density was slightly higher for the putatively excitatory boutons than for the inhibitory ones. When taken together with previous analyses of jaw-closing alpha-motoneurons the present data on jaw-opening alpha-motoneurons indicate that the two types of neuron differ in regard to the nature of synaptic integration in the dendritic tree.
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Affiliation(s)
- Y Shigenaga
- Department of Oral Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Jung-Gu, Daegu 700-412, Korea.
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Romanelli P, Esposito V, Schaal DW, Heit G. Somatotopy in the basal ganglia: experimental and clinical evidence for segregated sensorimotor channels. ACTA ACUST UNITED AC 2005; 48:112-28. [PMID: 15708631 DOI: 10.1016/j.brainresrev.2004.09.008] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2004] [Indexed: 11/22/2022]
Abstract
Growing experimental and clinical evidence supports the notion that the cortico-basal ganglia-thalamo-cortical loops proceed along parallel circuits linking cortical and subcortical regions subserving the processing of sensorimotor, associative and affective tasks. In particular, there is evidence that a strict topographic segregation is maintained during the processing of sensorimotor information flowing from cortical motor areas to the sensorimotor areas of the basal ganglia. The output from the basal ganglia to the motor thalamus, which projects back to neocortical motor areas, is also organized into topographically segregated channels. This high degree of topographic segregation is demonstrated by the presence of a well-defined somatotopic organization in the sensorimotor areas of the basal ganglia. The presence of body maps in the basal ganglia has become clinically relevant with the increasing use of surgical procedures, such as lesioning or deep brain stimulation, which are selectively aimed at restricted subcortical targets in the sensorimotor loop such as the subthalamic nucleus (STN) or the globus pallidus pars interna (GPi). The ability to ameliorate the motor control dysfunction without producing side effects related to interference with non-motor circuits subserving associative or affective processing requires the ability to target subcortical areas particularly involved in sensorimotor processing (currently achieved only by careful intraoperative microelectrode mapping). The goal of this article is to review current knowledge about the somatotopic segregation of basal ganglia sensorimotor areas and outline in detail what is known about their body maps.
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Garcia L, D'Alessandro G, Bioulac B, Hammond C. High-frequency stimulation in Parkinson's disease: more or less? Trends Neurosci 2005; 28:209-16. [PMID: 15808356 DOI: 10.1016/j.tins.2005.02.005] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Deep-brain stimulation at high frequency is now considered the most effective neurosurgical therapy for movement disorders. An electrode is chronically implanted in a particular area of the brain and, when continuously stimulated, it significantly alleviates motor symptoms. In Parkinson's disease, common target nuclei of high-frequency stimulation (HFS) are ventral thalamic nuclei and basal ganglia nuclei, such as the internal segment of the pallidum and the subthalamic nucleus (STN), with a preference for the STN in recent years. Two fundamental mechanisms have been proposed to underlie the beneficial effects of HFS: silencing or excitation of STN neurons. Relying on recent experimental data, we suggest that both are instrumental: HFS switches off a pathological disrupted activity in the STN (a 'less' mechanism) and imposes a new type of discharge in the upper gamma-band frequency that is endowed with beneficial effects (a 'more' mechanism). The intrinsic capacity of basal ganglia and particular STN neurons to generate oscillations and shift rapidly from a physiological to a pathogenic pattern is pivotal in the operation of these circuits in health and disease.
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Affiliation(s)
- Liliana Garcia
- Laboratoire de neurophysiologie (Centre National de la Recherche Scientifique UMR 5543), Université de Bordeaux 2,146 rue Léo Saignat, 33076 Bordeaux Cedex, France
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36
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Rodríguez Díaz M, Alonso TJ, Perdomo Diaz J, Gonzalez Hernández T, Castro Fuentes R, Sabate M, Garcia Dopico J. Glial regulation of nonsynaptic extracellular glutamate in the substantia nigra. Glia 2005; 49:134-42. [PMID: 15390097 DOI: 10.1002/glia.20100] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
GLU is the main neurotransmitter in the brain, where it induces a synaptic excitatory action. There is recent evidence for an extracellular nonsynaptic GLU (EnS-GLU) pool in different brain nuclei that, released from glial cells, may act on extrasynaptic GLU receptors of cells located far from the position in which it was released. In the present work, the EnS-GLU pool was studied with microdialysis in the rat substantia nigra (SN). We observed an EnS-GLU pool that increased in a Ca2+-dependent manner during cell depolarization. The selective alteration of with methionine sulfoximide (MSO) and fluorocitrate induced marked modifications in EnS-GLU suggesting that EnS-GLU is dependent on glial cells. Glutamine administration increased GLU, suggesting that neurons are also involved in EnS-GLU modulation. GLU administered in the rostral SN showed a long-distance diffusion to the caudal SN. The ionotropic GLU receptors agonist N-methyl-D-aspartate and kainate and the metabotropic GLU receptors agonist ACPD increased EnS-GLU and decreased extracellular glutamine. Taken together, these data indicate that nigral glia releases GLU, which probably performs a volume transmitter role.
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Affiliation(s)
- Manuel Rodríguez Díaz
- Laboratory of Neurobiology and Experimental Neurology, Department of Physiology, University of La Laguna, La Laguna, Tenerife, Canary Islands, Spain.
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Boyes J, Bolam JP. The subcellular localization of GABA(B) receptor subunits in the rat substantia nigra. Eur J Neurosci 2004; 18:3279-93. [PMID: 14686901 DOI: 10.1111/j.1460-9568.2003.03076.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The inhibitory effects of GABA within the substantia nigra (SN) are mediated in part by metabotropic GABA(B) receptors. To better understand the mechanisms underlying these effects, we have examined the subcellular localization of the GABA(B) receptor subunits, GABA(B1) and GABA(B2), in SN neurons and afferents using pre-embedding immunocytochemistry combined with anterograde or retrograde labelling. In both the SN pars compacta (SNc) and pars reticulata (SNr), GABA(B1) and GABA(B2) showed overlapping, but distinct, patterns of immunolabelling. GABA(B1) was more strongly expressed by putative dopaminergic neurons in the SNc than by SNr projection neurons, whereas GABA(B2) was mainly expressed in the neuropil of both regions. Immunogold labelling for GABA(B1) and GABA(B2) was localized in presynaptic and postsynaptic elements throughout the SN. The majority of labelling was intracellular or was associated with extrasynaptic sites on the plasma membrane. In addition, labelling for both subunits was found on the presynaptic and postsynaptic membranes at symmetric, putative GABAergic synapses, including those formed by anterogradely labelled striatonigral and pallidonigral terminals. Labelling was also observed on the presynaptic membrane and at the edge of the postsynaptic density at asymmetric, putative excitatory synapses. Double immunolabelling, using the vesicular glutamate transporter 2, revealed the glutamatergic nature of many of the immunogold-labelled asymmetric synapses. The widespread distribution of GABA(B) subunits in the SNc and SNr suggests that GABA(B)-mediated effects in these regions are likely to be more complex than previously described, involving presynaptic autoreceptors and heteroreceptors, and postsynaptic receptors on different populations of SN neurons.
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Affiliation(s)
- Justin Boyes
- MRC Anatomical Neuropharmacology Unit, University of Oxford, Oxford OX1 3TH, UK
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38
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Abstract
Although it is well known that high-frequency stimulation (HFS) of the subthalamic nucleus (STN) alleviates the cardinal symptoms of Parkinson's disease, the underlying mechanisms are not fully understood. We investigated the effect of stimulation from low to high frequencies on rat STN neurons in naive and dopamine-depleted slices using whole-cell, current-clamp techniques and on-line artifact suppression. Stimulation at 10 Hz evoked 10 Hz single spikes but did not significantly modify ongoing STN activity. In contrast, at therapeutically relevant frequencies (80-185 Hz), stimulation had a dual effect: it fully suppressed STN spontaneous activity and generated a robust pattern of recurrent bursts of spikes, with each spike being time-locked to a stimulus pulse. Neither the suppression of spontaneous activity nor the generation of spikes was prevented by the antagonists of the metabotropic and ionotropic receptors of glutamate and gamma-aminobutyric acid. Tetrodotoxin, the Na+ channel blocker, suppressed all HFS-evoked spikes, whereas nifedipin, an L-type Ca2+-channel blocker, abolished the membrane oscillations underlying bursts. Therefore, we conclude that HFS drives the STN neuronal activity by directly activating the neuronal membrane. We suggest that this pattern may remove the deleterious activity of the basal ganglia network in the parkinsonian state and drive target neurons to a high-frequency state of activity, dependent on the characteristics of STN efferent synapses and resonant properties of target membranes.
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39
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Ragnarson B, Ornung G, Grant G, Ottersen OP, Ulfhake B. Glutamate and AMPA receptor immunoreactivity in Ia synapses with motoneurons and neurons of the central cervical nucleus. Exp Brain Res 2003; 149:447-57. [PMID: 12677325 DOI: 10.1007/s00221-003-1388-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2002] [Accepted: 12/21/2002] [Indexed: 12/22/2022]
Abstract
Axonal tracing and high resolution immunocytochemistry were used to identify transmitter content and postsynaptic receptors in synapses between Ia primary afferents and motoneurons and in neurons of the central cervical nucleus (CCN), respectively, in the rat. The terminals, as well as the target neurons, were identified by postembedding immunogold detection of transganglionically or retrogradely, respectively, transported cholera toxin B subunit (CTB), and in adjacent sections postembedding immunogold was employed to demonstrate glutamate and AMPA receptors in the same synapses. A total of 390 CTB-labelled Ia boutons in apposition to CTB-labelled motoneurons, CCN neurons or unlabelled dendrites in the surrounding neuropil were traced in section series from two animals. A third animal was used as a control. In the motor nucleus, a majority of the synapses were with medium-sized dendrites, whereas in the CCN the distribution was skewed towards fine-calibre dendrites. In both nuclei, somatic and juxtasomatic synapses were quite infrequent (<10%). All of the CTB-labelled Ia boutons recovered in the sections incubated for glutamate (n=323) were enriched with glutamate immunoreactivity. One hundred and fifty of these disclosed synaptic contact in at least two ultrathin sections. In this sample, 50% (33-59%) appeared immunoreactive to receptor sub-units GluR1-4 in at least two ultrathin sections, whereas 35% were labelled in one section only. Distribution of gold particles relative to presynaptic and postsynaptic membrane profiles (n=23) revealed a close correlation between AMPA immunoreactivity and the postsynaptic membrane of the synapse. Finally, immunogold particles signalling GluR1 were observed much less frequently than particles signalling GluR2/3 or GluR4. Our results provide additional strong evidence that chemical transmission at Ia synapses is mediated by glutamate and identify GluR2/3 and GluR4 as important postsynaptic receptors.
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Affiliation(s)
- Birger Ragnarson
- Experimental Neurogerontology, Department of Neuroscience, The Retzius Laboratory, Karolinska Institutet, 171 77 Stockholm, Sweden
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40
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Luo J, Kaplitt MG, Fitzsimons HL, Zuzga DS, Liu Y, Oshinsky ML, During MJ. Subthalamic GAD gene therapy in a Parkinson's disease rat model. Science 2002; 298:425-9. [PMID: 12376704 DOI: 10.1126/science.1074549] [Citation(s) in RCA: 249] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The motor abnormalities of Parkinson's disease (PD) are caused by alterations in basal ganglia network activity, including disinhibition of the subthalamic nucleus (STN), and excessive activity of the major output nuclei. Using adeno-associated viral vector-mediated somatic cell gene transfer, we expressed glutamic acid decarboxylase (GAD), the enzyme that catalyzes synthesis of the neurotransmitter GABA, in excitatory glutamatergic neurons of the STN in rats. The transduced neurons, when driven by electrical stimulation, produced mixed inhibitory responses associated with GABA release. This phenotypic shift resulted in strong neuroprotection of nigral dopamine neurons and rescue of the parkinsonian behavioral phenotype. This strategy suggests that there is plasticity between excitatory and inhibitory neurotransmission in the mammalian brain that could be exploited for therapeutic benefit.
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Affiliation(s)
- Jia Luo
- Functional Genomics and Translational Neuroscience Laboratory, Department of Molecular Medicine and Pathology, University of Auckland, Auckland, New Zealand
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41
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Activation of ventral tegmental area cells by the bed nucleus of the stria terminalis: a novel excitatory amino acid input to midbrain dopamine neurons. J Neurosci 2002. [PMID: 12077212 DOI: 10.1523/jneurosci.22-12-05173.2002] [Citation(s) in RCA: 189] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We examined the role of excitatory amino acids (EAAs) in the activation of midbrain dopaminergic (DA) neurons evoked by stimulation of the ventromedial and ventrolateral (subcommissural) bed nucleus of the stria terminalis (vBNST). Using anesthetized rats and extracellular recording techniques, we found that 84.8% of ventral tegmental area (VTA) DA neurons were activated synaptically by single-pulse electrical stimulation of the vBNST. In contrast, similar stimulation did not affect the activity of presumed GABA neurons in the VTA. Three characteristic responses were observed in VTA DA neurons: short latency activation (<25 msec; 55.1% of cells), long latency activation (>65 msec; 56% of cells), and inhibition (61.8% of cells, usually followed by long latency excitation). Microinfusion of antagonists of EAA receptors (3 mm kynurenic acid, 100 microm AP-5, or 50 microm CNQX) from a micropipette adjacent to the recording electrode significantly reduced both short and long latency activations evoked in DA neurons by vBNST stimulation. Specific responses were attenuated similarly by AP-5 alone, CNQX alone, or a cocktail of AP-5+CNQX, indicating that joint activation of NMDA plus non-NMDA receptors was required. Stimulation of the vBNST by local microinfusion of glutamate increased the firing and bursting activity of VTA DA neurons. Similar microinfusion of GABA decreased bursting of VTA DA neurons without altering their firing rate. Retrograde and anterograde labeling and antidromic activation of vBNST neurons by VTA stimulation confirmed a direct projection from the vBNST to the VTA. These results reveal that inputs from the vBNST exert a strong excitatory influence on VTA DA neurons mediated by both NMDA and non-NMDA receptors.
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Abstract
Four organizational levels of the basal ganglia that could be particularly determinant in terms of functional properties are reviewed: (1) macroscopic anatomy, which is characterized by a dramatic decrease of cerebral tissue volume from the cerebral cortex to the deepest portions of the basal ganglia; (2) connectivity, which consists of both complex loops and a partition into three territories, sensorimotor, associative, and limbic (which process motor, cognitive, and emotional information, respectively); (3) neuronal morphology, characterized by a dramatic numeric and geometric convergence of striatal neurons onto pallidonigral neurons; and (4) dopaminergic innervation of the basal ganglia, which is organized as a dual system that is supposed to have opposite effects on the activity of the system. Current models of the basal ganglia are discussed.
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Affiliation(s)
- J Yelnik
- Institut National de la Santé et de la Recherche Médicale U289, Hôpital de la Salpêtrière, Paris, France.
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43
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Chen BT, Rice ME. Synaptic regulation of somatodendritic dopamine release by glutamate and GABA differs between substantia nigra and ventral tegmental area. J Neurochem 2002; 81:158-69. [PMID: 12067228 DOI: 10.1046/j.1471-4159.2002.00811.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Midbrain dopamine (DA) cells of the substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA) exhibit somatodendritic release of DA. To address how somatodendritic release is regulated by synaptic glutamatergic and GABAergic input, we examined the effect of ionotropic-receptor antagonists on locally evoked extracellular DA concentration ([DA]o) in guinea pig midbrain slices. Evoked [DA]o was monitored with carbon-fiber microelectrodes and fast-scan cyclic voltammetry. In SNc, evoked [DA]o was 160% of control in the presence of the AMPA-receptor antagonist, GYKI-52466, or the NMDA-receptor antagonist, AP5. Similar increases were seen with the GABAA-receptor antagonist, picrotoxin, or the GABA(B)-receptor antagonist, saclofen. The increase seen with GYKI-52466 was prevented when both picrotoxin and saclofen were present, consistent with normal, AMPA-receptor mediated activation of GABAergic inhibition. The increase with AP5 persisted, however, implicating NMDA-receptor mediated activation of another inhibitory circuit in SNc. In the VTA, by contrast, evoked [DA]o was unaffected by GYKI-52466 and fell slightly with AP5. Neither picrotoxin nor saclofen alone or in combination had a significant effect on evoked [DA]o. When GABA receptors were blocked in the VTA, evoked [DA]o was decreased by 20% with either GYKI-52466 or AP5. These data suggest that in SNc, glutamatergic input acts predominantly on GABAergic or other inhibitory circuits to inhibit somatodendritic DA release, whereas in VTA, the timing or strength of synaptic input will govern whether the net effect on DA release is excitatory or inhibitory.
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Affiliation(s)
- Billy T Chen
- Department of Physiology and Neuroscience, New York University School of Medicine, New York 10016, USA
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44
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Bevan MD, Magill PJ, Hallworth NE, Bolam JP, Wilson CJ. Regulation of the timing and pattern of action potential generation in rat subthalamic neurons in vitro by GABA-A IPSPs. J Neurophysiol 2002; 87:1348-62. [PMID: 11877509 DOI: 10.1152/jn.00582.2001] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The regulation of activity in the subthalamic nucleus (STN) by GABAergic inhibition from the reciprocally connected globus pallidus (GP) plays an important role in normal movement and disorders of movement. To determine the precise manner in which GABAergic synaptic input, acting at A-type receptors, influences the firing of STN neurons, we recorded the response of STN neurons to GABA-A inhibitory postsynaptic potentials (IPSPs) that were evoked by supramaximal electrical stimulation of the internal capsule using the perforated-patch technique in slices at 37 degrees C. The mean equilibrium potential of the GABA-A IPSP (EGABA-A IPSP) was -79.4 +/- 7.0 mV. Single IPSPs disrupted the spontaneous oscillation that underlies rhythmic single-spike firing in STN neurons. As the magnitude of IPSPs increased, the effectiveness of prolonging the interspike interval was related more strongly to the phase of the oscillation at which the IPSP was evoked. Thus the largest IPSPs tended to reset the oscillatory cycle, whereas the smallest IPSPs tended to produce relatively phase-independent delays in firing. Multiple IPSPs were evoked at various frequencies and over different periods and their impact was studied on STN neurons held at different levels of polarization. Multiple IPSPs reduced and/or prevented action potential generation and/or produced sufficient hyperpolarization to activate a rebound depolarization, which generated a single spike or restored rhythmic spiking and/or generated a burst of activity. The pattern of IPSPs and the level of polarization of STN neurons were critical in determining the nature of the response. The duration of bursts varied from 20 ms to several hundred milliseconds, depending on the intrinsic rebound properties of the postsynaptic neuron. These data demonstrate that inhibitory input from the GP can produce a range of firing patterns in STN neurons, depending on the number and frequencies of IPSPs and the membrane properties and voltage of the postsynaptic neuron.
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Affiliation(s)
- M D Bevan
- Department of Anatomy and Neurobiology, University of Tennessee, Rm. 515 Link, 855 Monroe Avenue, Memphis, TN 38163, USA.
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45
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Bianchi L, Colivicchi MA, Frosini M, Palmi M, Della Corte L. The effect of kainic acid and AMPA on the release of taurine and GABA from the rat substantia nigra in vivo. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 483:293-6. [PMID: 11787610 DOI: 10.1007/0-306-46838-7_32] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- L Bianchi
- Dip. di Farmacologia Preclinica e Clinica M. Aiazzi Mancini, Universitá di Firenze, Italy
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46
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Marti M, Guerrini R, Beani L, Bianchi C, Morari M. Nociceptin/orphanin FQ receptors modulate glutamate extracellular levels in the substantia nigra pars reticulata. A microdialysis study in the awake freely moving rat. Neuroscience 2002; 112:153-60. [PMID: 12044480 DOI: 10.1016/s0306-4522(02)00050-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Intracerebral microdialysis was employed in awake freely moving rats to investigate the effects of nociceptin/orphanin FQ receptor ligands on glutamate extracellular levels in the substantia nigra pars reticulata. Nociceptin/orphanin FQ, ineffective at 0.1 microM, induced a prolonged stimulation of nigral glutamate levels at 1 and 10 microM (mean effect of 137+/-9 and 167+/-13%, respectively, of basal values). These effects were prevented by the novel nociceptin/orphanin FQ receptor antagonist [Nphe(1)]nociceptin/orphanin FQ(1-13)NH(2) (100 and 300 microM, respectively) but not by the non-selective opioid receptor antagonist naloxone (10 microM). [Nphe(1)]nociceptin/orphanin FQ(1-13)NH(2) (100 microM) inhibited by itself glutamate outflow (maximal reduction to 71+/-4%) while naloxone was ineffective. The nociceptin/orphanin FQ receptor ligand [Phe(1)psi(CH(2)-NH)Gly(2)]nociceptin/orphanin FQ(1-13)NH(2) also facilitated glutamate outflow at 10 microM (mean effect of 145+/-10%). Intranigral perfusion with tetrodotoxin (1 microM) or with the dopamine D(2) receptor antagonist raclopride (1 microM), failed to affect basal glutamate output and prevented the facilitatory effect of nociceptin/orphanin FQ (10 microM). However, perfusion with the GABA(A) receptor antagonist bicuculline (10 microM) increased local glutamate extracellular levels by itself and attenuated the effect of the peptide. Our data suggest that nociceptin/orphanin FQ increases glutamate extracellular levels in the substantia nigra pars reticulata via activation of nociceptin/orphanin FQ receptors located on non-glutamatergic, possibly dopaminergic and GABAergic, neuronal elements.
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Affiliation(s)
- M Marti
- Department of Experimental and Clinical Medicine, Section of Pharmacology, University of Ferrara, via Fossato di Mortara 17-19, 44100 Ferrara, Italy
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47
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Abstract
Tourette's syndrome is a neuropsychiatric syndrome with onset in childhood that is characterized by chronic multiple tics. The cause of Tourette's syndrome is unknown, but the pathophysiology most likely involves basal ganglia and frontocortical circuits. A useful scheme of basal ganglia dysfunction should be able to account for the features that make Tourette's syndrome unique, in addition to the features that Tourette's syndrome shares with other disorders. Recent advances in knowledge of basal ganglia functional anatomy and physiology make it possible to hypothesize how specific neural mechanisms relate to specific clinical manifestations of Tourette's syndrome. A model of selection and suppression of competing behaviors by the basal ganglia is presented. The functional anatomy of basal ganglia circuits and new information on dopamine modulation of those circuits provide the basis for hypotheses of basal ganglia dysfunction in Tourette's syndrome.
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Affiliation(s)
- J W Mink
- Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
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48
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Abstract
Hallervorden-Spatz syndrome (HSS) is a degenerative neurologic disorder associated with progressive rigidity, dystonia, impaired voluntary movement, dysarthria, and mental deterioration. Pathologically, there is iron deposition in the basal ganglia, with destruction of basal ganglia output neurons. Recent advances in the understanding of basal ganglia functional anatomy and physiology make it possible to hypothesize how specific neural mechanisms relate to specific clinical manifestations of HSS. Experimental lesions of the basal ganglia output nucleic cause involuntary muscle contractions, similar to contractions observed in dystonia. A model of selection and suppression of competing motor patterns by the basal ganglia is presented in relation to the manifestations of damage to basal ganglia output neurons. It is hypothesized that the dystonia and other motor abnormalities seen in HSS can be attributed to degeneration of basal ganglia output neurons.
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Affiliation(s)
- J W Mink
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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49
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Ferraro L, Tomasini MC, Fernandez M, Bebe BW, O'Connor WT, Fuxe K, Glennon JC, Tanganelli S, Antonelli T. Nigral neurotensin receptor regulation of nigral glutamate and nigroventral thalamic GABA transmission: a dual-probe microdialysis study in intact conscious rat brain. Neuroscience 2001; 102:113-20. [PMID: 11226674 DOI: 10.1016/s0306-4522(00)00448-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Dual-probe microdialysis in the awake rat was employed to investigate the effects of intranigral perfusion with the tridecapeptide neurotensin on local dialysate glutamate and GABA levels in the substantia nigra pars reticulata and on dialysate GABA levels in the ventral thalamus. Intranigral neurotensin (10-300nM, 60min) dose-dependently increased (+29+/-3% and +46+/-3% vs basal for the 100 and 300nM concentrations, respectively) local dialysate glutamate levels, while the highest 300nM concentration of the peptide exerted a long-lasting and prolonged reduction in both local and ventral thalamic (-20+/-4% and -22+/-2%, respectively) GABA levels. Intranigral perfusion with the inactive neurotensin fragment neurotensin(1-7) (10-300nM, 60min) was without effect. Furthermore, the non-peptide neurotensin receptor antagonist SR 48692 (0.2mg/kg) and tetrodotoxin (1microM) fully counteracted the intranigral neurotensin (300nM)-induced increase in local glutamate. SR 48692 (0.2mg/kg) also counteracted the decreases in nigral and ventral thalamic GABA release induced by the peptide. In addition, intranigral perfusion with the dopamine D(2) receptor antagonist raclopride (1microM) fully antagonized the neurotensin (300nM)-induced decreases in nigral and ventral thalamic GABA levels. The ability of nigral neurotensin receptor activation to differently influence glutamate and GABA levels, whereby it increases nigral glutamate and decreases both nigral and ventral thalamic GABA levels, suggests the involvement of neurotensin receptor in the regulation of basal ganglia output at the level of the nigra.
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Affiliation(s)
- L Ferraro
- Department of Clinical and Experimental Medicine, Section of Pharmacology, University of Ferrara, Via Fossato di Mortara 17-19, 44100, Ferrara, Italy
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50
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Abstract
The subthalamic nucleus (STN) plays a crucial role as a regulator of basal ganglia outflow by providing excitatory glutamatergic input into the two output nuclei of the basal ganglia, substantia nigra pars reticulata (SNpr), and entopeduncular nucleus. This study examined the effects of suppressing activity in the STN of the awake, behaving rat. Specifically, we evaluated the effects of unilateral and bilateral focal inhibition of STN on posture, locomotion, and susceptibility to limbic motor seizures. Unilateral microinjection of a GABA(A) receptor agonist (muscimol, 200 pmol) into STN produced a site-dependent contralaterally directed postural asymmetry without locomotor activation. This effect differed from responses produced by the same dose of muscimol placed into SNpr, which included locomotor activation in addition to contralaterally directed postural asymmetry. Locomotor activation and postural asymmetry were obtained also after blockade of glutamate transmission in SNpr by the unilateral application of kynurenate (100 nmol). Our observation that STN inhibition did not induce the locomotor activation characteristic of SNpr inhibition suggests that there are glutamatergic inputs to SNpr, other than those from STN, that are responsible for controlling locomotion. Bilateral, but not unilateral, injection of muscimol (200 pmol) into STN protected against limbic motor seizures evoked either by intravenous bicuculline or by focal application of bicuculline into anterior piriform cortex (area tempestas). These results demonstrate that focal inhibition of STN reproduces the postural asymmetry and anticonvulsant actions that are obtained with the inhibition of SNpr. This provides behavioral support for the concept that STN contributes a crucial tonic excitatory (glutamatergic) drive to the rat SNpr.
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